Splitting Cooper pairs

Henning Soller

A superconductor connected to normal leads allows to generate Einstein–Podolsky–Rosen pairs by Cooper pair splitting (CPS). It has been realized with quantum dots either defined in carbon nanotubes or InAs nanowires. After establishing the presence of CPS in such devices new works have investigated the effects of a finite potential difference between the quantum dots to improve and characterize the efficiency of CPS. In this paper, we present a generic model for CPS and develop two minimal models specifically for the two experimental realizations and compare them to the experimental data. In addition, we also explore the relation of nonlocal charge transfer to positive current cross-correlation of currents and discuss the temperature dependence of CPS.

Antti Ranni, Fredrik Brange, Elsa T. Mannila +2 more

Controlled generation and detection of quantum entanglement between spatially separated particles constitute an essential prerequisite both for testing the foundations of quantum mechanics and for realizing future quantum technologies. Splitting of Cooper pairs from a superconductor provides entangled electrons at separate locations. However, experimentally accessing the individual split Cooper pairs constitutes a major unresolved issue as they mix together with electrons from competing processes. Here, we overcome this challenge with the first real-time observation of the splitting of individual Cooper pairs, enabling direct access to the time-resolved statistics of Cooper pair splitting. We determine the correlation statistics arising from two-electron processes and find a pronounced peak that is two orders of magnitude larger than the background. Our experiment thereby allows to unambiguously pinpoint and select split Cooper pairs with 99% fidelity. These results open up an avenue for performing experiments that tap into the spin-entanglement of split Cooper pairs.

David Abergel

Antti Ranni, Fredrik Brange, E. T. Mannila +2 more

Abstract Controlled generation and detection of quantum entanglement between spatially separated particles constitute an essential prerequisite both for testing the foundations of quantum mechanics and for realizing future quantum technologies. Splitting of Cooper pairs from a superconductor provides entangled electrons at separate locations. However, experimentally accessing the individual split Cooper pairs constitutes a major unresolved issue as they mix together with electrons from competing processes. Here, we overcome this challenge with the first real-time observation of the splitting of individual Cooper pairs, enabling direct access to the time-resolved statistics of Cooper pair splitting. We determine the correlation statistics arising from two-electron processes and find a pronounced peak that is two orders of magnitude larger than the background. Our experiment thereby allows to unambiguously pinpoint and select split Cooper pairs with 99% fidelity. These results open up an avenue for performing experiments that tap into the spin-entanglement of split Cooper pairs.

G. Potel, Ricardo A. Broglia